Switched mode power supplies (SMPS) are electronic power supplies that convert power more efficiently than traditional power supplies. Unlike these other power supplies, SMPS use switching regulators to repeatedly switch between low-power-dissipation on and off states and to avoid high-power-dissipation states altogether, thereby conserving energy. For example, the power stage of a SMPS—which performs voltage rectification—may use one or more metal oxide semiconductor field effect transistor (MOSFET) switches in lieu of (or in tandem with) traditional, standard diodes or Schottky rectifiers, thus taking advantage of the relatively low voltage drop associated with the MOSFETs to increase energy efficiency. Such use of MOSFETs in SMPS power stages is called “synchronous rectification” (SR).
Despite their superior energy efficiency, the use of SR MOSFETs still presents multiple difficulties as a result of the application of inappropriate voltages to the MOSFET gates. For instance, during light load conditions the current draw from the SMPS is low, and in such conditions it may be advantageous to stop MOSFET switching or to at least reduce the MOSFET gate input voltage. Current SMPS, however, do not provide the ability to dynamically adjust the MOSFET gate input voltage to an appropriate level and to subsequently maintain that level. Similarly, if a SMPS power stage uses a SR MOSFET in tandem with a traditional diode or Schottky rectifier, the transition between standard rectification and synchronous rectification should be carefully controlled so that it is gradual and even, avoiding sudden voltage spikes that can result in system instability. This, too, may be accomplished by precisely and dynamically controlling the MOSFET gate input voltage. Such precise, dynamic voltage control may also prevent damage to MOSFET switches, such as gallium nitride FETs that have very low threshold voltages required for current to flow between source and drain. As mentioned, however, at present there is no suitable technique for precisely and dynamically adjusting and subsequently maintaining the gate input voltage provided to SR MOSFETs in the context of SMPS power stages.